Neuronal apoptosis associated with basic fibroblast growth factor and its receptor following cerebral ischemia reperfusion / 中国组织工程研究

ABSTRACT

BACKGROUND: Brain injury can induce the increased expression of basic fibroblast growth factor (bFGF) in brain,whereas FGFR is a very important player in the cell proliferation and differentiation, angiogenesis, skeletogeny, etc.OBJECTIVE: To observe the effect of bFGF and its receptor on neuronal apoptosis following cerebral ischemia/reperfusion injury in rats.DESIGN: A randomized grouping design and animal experiment.SETTING: Institute of Cerebrovascular Disease, Affiliated Hospital of Qingdao University Medical College.MATERIALS: Twenty-eight healthy adult Wistar rats of clean degree, weighing 220-260 g, were provided by the experimental animal center of Shandong University. Rabbit-anti-rat bFGF and fibroblast growth factor receptor-1(FGFR-1) monoclonal antibodies were provided by Wuhan Boster Biological Technology, Co.,Ltd.METHODS: The experiment was carried out in Shandong Key Laboratory for Prevention and Treatment of Brain diseases.① The rats were randomly divided into experimental group (n =24) and sham-operated group (n =4). Models of middle cerebral artery occlusion/reperfusion (MCAO/R) were established by thread occlusion via left external-internal carotid arteries, and 4 rats in the experimental group were sampled at 1-hour ischemia/6, 12-hour, 1, 3, 7 and 14-day reperfusion respectively. The rats in the sham-operated group were given the same treatment without inserting thread.After anesthesia, the brain was removed completely by cutting head, then the brain tissue at about 5 mm posterior to optic chiasma was cut down, then serial coronal sections (5 μm) were prepared. ② The brain tissues were stained with ematoxylin-eosin (HE), and the forms of neurons were observed under microscope. ③ TdT-mediated dUTP-biotin nick end labeling (TUNEL) method: there were buffy granules in nucleus which was positively stained (apoptosis). Four fields were randomly selected from cortex and striatum to count positive cells under high-power microscope (×400). ④ The sections were stained with rabbit-anti-rat bFGF and FGFR-1 monoclonal antibodies, 4 fields were randomly selected from cortex and striatum to count positive cells under high-power microscope (×400).MAIN OUTCOME MEASURES: Apoptosis and the expressions of bFGF and FGFR-1.RESULTS: All the 28 rats were involved in the analysis of results. ① In the experimental group, the neurons in the ischemic sites were obviously decreased, some neurons appeared as paryopyknosis and became irregular, also deeply stained as purplish blue, nucleolus disappeared, and there were many scattered cellular fragments. ② In the sham-operated group, there were a few apoptotic neurons in the brain tissue, and the apoptotic neurons were obviously increased after ischemia, which mainly observed in cortexes and striatums of frontal and paritetal lobes. In the experimental group, apoptotic cells in cortexes began to increase gradually at 6 hours, and there were more cells at 12hours and 3 days, which reached the peak value at 1 day, and began to decrease at 3 day, but there were still more apoptotic cells at 14 days than in the sham-operated group. The number of apoptotic neurons and the changing trend in striatums were generally the same as those in cortexes (P ＞ 0.05). ③ In the sham-operated group, there were weak bFGF expression in the neurons of brain tissue, but there were fewer lightly stained positive cells. After cerebral ischemia, the bFGF expressions were increased, mainly observed in cortexes and striatums. The bFGF expression appeared at 6 hours after cerebral ischemia/reperfusion, and the number was increased gradually and deeply stained as the time of reperfusion prolonged (Figure 3), it reached the peak value at 1-3 days, and then weakened gradually, but it was still higher than in the sham-operated group at 14 days [(5.01 ±1.71), (5.21 ± 1.62) cells/visual field; (2.03± 1.73),(2.46± 1.38) cells/visual field, P ＜ 0.05]. ④ In the sham-operated group, lightly stained FGFR-1 positive cells could be observed in brain tissue. At 6 hours after cerebral ischemia/reperfusion, the FGFR positive cells began to increased in cortexes and striatums, which were the most at 1-3 days, and gradually decreased after 3 days, and the number was still a little more than that in the sham-operated group at 14 days [(5.01± 1.41), (5.20± 1.33) cells/visual field; (2.25±1.67),(2.32± 1.61 ) cells/visual field].CONCLUSION: After cerebral ischemia/reperfusion, the expressions of endogenous bFGF and FGFR-1 may be activated in cortex and striatum, then inhibit the neuronal apoptosis, and play its neuroprotective role.